Fix x64 detection, Win7 PowerShell 3.0 prompt and other issues
* .Contains() cannot be used with PowerShell 2.0 (Win7 default), which prevents
the prompt that asks users to install PowerShell 3.0 from being displayed...
* Fix LTR display of Windows Releases for RTL languages.
* $env:PROCESSOR_ARCHITECTURE reports the architecture of the PowerShell runtime
rather than the one from the OS, meaning that when executed in 32-bit mode on
a 64-bit system (like with Rufus) it will report X86 instead of AMD64.
Use [Environment]::Is64BitOperatingSystem instead.
* Closes #5